This invention relates to recuperators and particularly to the configuration of an annular recuperator for enhancing heat transfer and in another embodiment this invention includes a by-pass system for by-passing the annular recuperator for boosting the temperature of the heat transfer medium being utilized for other components in a microturbine system.
This invention constitutes an improvement over the annular recuperator structure disclosed in co-pending patent application Ser. No. 09/934,640 filed on Aug. 22, 2001 by William R. Ryan entitled RECUPERATOR FOR USE WITH TURBINE/TURBO-ALTERNATOR, published on Dec. 20, 2001, and commonly assigned to the assignee of this patent application. As shown in this patent, the recuperator includes a heat exchange structure where the compressor discharge air is placed in indirect heat exchange with the turbine exhaust prior to being injected into the ambient. The problem with this heretofore known recuperator is that after the turbine exhaust has been spent in the heat exchanger it is discharged into ambient in such a manner that the heat exchange is not as efficient as it should be, leaving a deficit in the heat exchange efficiency between the mediums. Also, there is no mechanism or concern disclosed in the Ryan patent application for utilizing the turbine exhaust prior to being placed in indirect heat relation in the recuperator and hence, that system lacks the ability to boost the temperature of other components in the microturbine system or match efficiencies from manufactured engine to engine that have varying efficiencies owing to manufacturing tolerances.
I have found that by encapsulating the recuperator with the spent exhaust gas exiting the recuperator, less heat in the heat exchange process of the recuperator is rejected prior to the heat recovery for which the recuperator is designed. Also, because the annular exhaust opening is annular and surrounds the recuperator core, this arrangement provides uniform circumferential back pressure, thus, resulting in a more even exhaust flow distribution and hence, higher effectiveness. Essentially, the essence of this invention is to provide an improved the discharge passage for the exhaust discharging from the recuperator in order to enhance the heat transfer efficiency of the fluids that are in indirect heat exchange relation in the recuperator.
In addition, this invention contemplates the option of including a by-pass system which may or may not be modulated that serves to power a co-generator system or boost the temperature of the heat exchange medium. In another application of the by-pass system, in order to assure that each of the engines manufactured has the same efficiency rating, the system is designed so that the by-pass is utilized to control the discharge of the turbine so as to trim each engine in order to match the engine""s efficiency which would otherwise be different owing to manufacturing tolerances.
An object of this invention is to provide for an annular recuperator of a microturbine system, means for encapsulating the recuperator with spent turbine exhaust so as to reduce heat losses within the recuperator. In addition, the annular design of the exhaust of the recuperator serves to provide a uniform circumferential back pressure, with a consequential evening or, in the very least, having the propensity for evening, the exhaust flow distribution which results in an increase in heat exchange transfer effectiveness and hence, an increase in heat transfer efficiency.
Another object of this invention is to provide a by-pass valve judiciously located in the recuperator for powering a co-generating system with turbine waste heated fluid discharging from the turbine and by-passing the recuperator. The by-pass can be operated either manually or automatically so as to provide a predetermined heat exchange relationship in the co-generation system.
A still further object of this invention is to provide an adjustable by-pass valve associated with the recuperator for trimming the efficiency of the microturbine engine whose efficiency is subjected to manufacturing tolerances so as to match a predetermined value.
The foregoing and other features of the present invention will become more apparent from the following description and accompanying drawings.